The present invention relates to dry, stable bleaching compositions comprising a sulfone peroxycarboxylic acid compound having surprising inherent properties providing active oxygen bleaching performance even after long storage periods.
The property possessed by some materials to bleach is known and widely used to remove discoloration or stains from articles. The behavior and mechanisms by which such bleaching agents perform their functions are only partially understood. It is known that many colored materials contain a conjugated chain, that is, a series of double bonds which alternate with single bonds. If one of the double bonds is eliminated the color is usually destroyed. Therefore, an agent which will remove a double bond linkage may be an effective bleach. A bleaching agent may also act on the groups at the end of the chain. Bleaching materials are generally categorized as chlorine, hypochlorites, chloramines, hydrogen peroxide and other peroxy compounds, chlorite and chlorine dioxide and reducing agents.
One well known category of bleaches comprises active chlorine releasing compounds. Bleaches in this category, while effective, have the disadvantages of tending to weaken or degrade fabrics or other materials, to react with other components of formulations containing them, to degrade the colors of many dyed fabrics or other colored articles and to cause yellowing of some synthetic or resin treated fabrics, etc.
The disadvantages of the active chlorine releasing bleaches are largely overcome by a second known category of bleaches referred to as inorganic oxygen bleaches comprising inorganic active oxygen releasing compounds. Bleaches in this category, while effective, have also exhibited significant disadvantages. For example, inorganic oxygen bleaches such as hydrogen peroxide, sodium perborate, sodium percarbonate, and the like, while often possessing good stability properties, all suffer the serious disadvantage that they must be used at a relatively high temperature such as 85.degree. C. or higher to be optimally effective in the absence of costly activators. A trend toward lower washing temperatures renders them unacceptable for use in many household washing machines which are now being operated at water temperatures less than about 60.degree. C. In general, effectiveness at lower temperatures would be advantageous because of reduced energy costs, reduced fabric damage or shrinkage, reduced need for sorting out temperature sensitive articles, etc.
To overcome the unsatisfactory low temperature performance of inorganic oxygen releasing compounds, it has been proposed that they be used in combination with so called bleach activators. Generally, these bleach activators are compounds which react with an inorganic oxygen bleach during the bleaching operation to release, in situ, a more reactive oxygen bleach such as a peroxycarboxylic acid. Several serious disadvantages are involved in the use of such combinations of inorganic oxygen bleaches with bleach activators. For example, in typical practice it is necessary to employ a large excess of either the inorganic oxygen releasing compound or the activator in order to obtain an acceptably complete and rapid release of the effective bleaching species. Another disadvantage is that the bleach activator must contain within its structure moieties which, upon release of the effective bleaching species, become side products. These side products contribute little or nothing to bleaching. Thus, the inclusion of these moieties tends to be wasteful.
All of the above-mentioned disadvantages of chlorine bleaches and inorganic oxygen bleaches used alone or in combination with activators can be overcome by the use of effective organic oxygen bleaches, particularly by the use of peroxycarboxylic acids. A number of such peroxycarboxylic acid bleaches are known in the art. However, these prior art peroxycarboxylic acids also exhibit some significant disadvantages. For example, due to their relatively high reactivity, these compounds tend to be difficult to maintain in an undegraded form during storage of products containing them, prior to their use. In some cases, it is impossible to achieve an acceptable shelf life. In other cases, it is necessary to use expensive stabilization systems which may consume large amounts of stabilizing materials. For example, if prior art peroxycarboxylic acid bleaches are incorporated into a complete detergent formulation, stabilization is possible only at substantial extra cost as by encapsulation or other means of ingredient segregation. Examples of prior art teaching the coating technique to isolate peroxycarboxylic acids are U.S. Pat. No. 3,847,830 to Williams et al, U.S. Pat. No. 4,094,808 to Stewart et al and U.S. Pat. No. 4,321,301 to Brichard et al.
Other consequences of inherent molecular instability of peroxycarboxylic acids include the need to blend them with components capable of absorbing energy during their decomposition in order to prevent violent decomposition. See for example U.S. Pat. No. 4,100,095 to Hutchins et al. A further disadvantage of some prior art peroxycarboxylic acids is a lack of selectivity in their bleaching action. Thus, in such cases, dyes on some colored articles are significantly damaged during bleaching, although usually not to as great an extent as with chlorine bleaches.
Because of the above disadvantages there is a continuing need for new peroxycarboxylic acid compounds, effective in bleaching, which overcome or reduce the disadvantages recited above for prior art compounds of this class.